A) 3
B) 5
C) 7
D) 1
Correct Answer: D
Solution :
\[f\left( x \right)={{x}^{7}}+14{{x}^{5}}+16{{x}^{3}}+30x-560\] \[f''\left( x \right)=7{{x}^{6}}+70{{x}^{4}}+48{{x}^{2}}+30>0\] \[\therefore \] \[f\] is increasing also \[\underset{x\to \infty }{\mathop{\lim }}\,f\left( x \right)=\infty \,;\,\underset{x\to -\infty }{\mathop{\lim }}\,f\left( x \right)=-\infty \] Clearly \[f\left( x \right)=0\] have exactly one real root.You need to login to perform this action.
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